After a landing WP is 'achieved' the nav controller seems to set motorsData.throttle to minimum value (1 or 0)remember that radio_throttle is in your control. Everything else goes through Nav controllerTry it on a mission. That's what happens.

The reason I was using two landing WPs was to have a quick way to lower altitude at the horizontal position of the last non landing WP.

I've used an 18 meter ROI on a landing WP in a mission that was flying at 6 m/s and it worked great. The quad had a nice curved landing. It lost altitude while still slowing down.

So I thought that 20 m/s might work just as well. All the WPs in the crash mission had 20 meter of ROI which let the quad make corners and not slow down. How ROI works is still a little confusing to me but I think when the quad is at 20 meters from the landing WP Nav controller uses some of the landing WP settings from the upcoming WP to control the quad.

My guess is that the motors being turned off was caused by the throttle being lowered as the quad started flying inside the ROI and by the time the quad was at the landing WP the throttle was low enough to trigger the disarming of the quad.

To stop a crash I think I can still use the two landing WPs but I'll have the ROI be at 1.5 meters and just to be sure there's no crashing a 5 second loiter on the last non landing WP would not hurt.

I will also need to add a 6 m/s WP before the landing WP to stop the quad from overshooting the landing WPs. Adjusting the Nav settings can stop the overshooting but those settings really slow down the acceleration.

It would be really nice to have a separate control for braking because a copter can brake at a much higher angle than used during acceleration and not lose altitude.

The large ROI keeps the overshooting of the corner WPs from being a problem when flying at 20 m/s. I still need to try 30 m/s so I can make use of a tail wind. The camera's for farm field photos work well at 30 m/s if there's bright sunlight.

In most of the US large farm areas flying from 200 to 400 feet is usually free of aircraft if you're not near an airport. During the growing season, spray planes are flying from 5 to 150 feet of altitude. It's much better to stay at a higher altitude and then come straight down as quickly as possible. I've tried to use a Takeoff WP with a negative number but that doesn't work. Using a normal WP to come straight down will let you descend at 2.5 m/s which is quite slow when you're at 120 meters.

The faster you can descend the less chance you have to be in the way of spray planes and the less battery capacity you use. I've tested the Field Eye at 10 m/s descending and that works quite well.

I could change the Nav Alt Position settings so I could have a much faster altitude change with a normal WP but that would also change the APH altitude control speed to be faster than I like.

Here's a look at the last few seconds of the crash log. It now looks to me that the combination of the large ROI and high descent speed caused the disarming of the motors or maybe just the descent rate of 10 m/s.